Drilling or grinding tools, more particularly for dental purposes



June 1956 E. HOFFMEISTER 2,748,483

DRILLING OR GRINDING TOOLS, MORE PARTICULARLY FOR DENTAL PURPOSES- Filed June 30, 1954 lNrz/vrole I.Ho1fmezstaz DRILLING OR GRINDING TOOLS, MORE PAR- TICULARLY FOR DENTAL PURPOSES Erich Holfmeister, Biberach-Riss, Germany Application June 30, 1954, Serial No. 440,401

Claims priority, application Germany July 3, 1953 1 Claim. (Cl. 3248) In the known drilling or grinding tools for dental purposes the cutting head, the tool shank and the clutch at the rear end of the tool shank consist of one piece.

Where the cutting head is made of hard metal, it has also been proposed to connect this cutting head of hard metal with the forward end of the tool shank in a suitable manner, for instance by soldering. In this Way it becomes unnecessary to make the whole tool shank and the clutch as well of the costly hard metal.

It has now been found, that due to the unavoidable lateral stressing of the tools which, moreover, project to a greater or less extent out of the bearing a breaking off of the cutting head itself frequently occurs at the point of connection with the shank, thereby rendering the drilling or grinding tool useless.

According to the invention this disadvantage may be avoided if the cutting head of hard metal or the diamond grinding member is fixed With a short shank on a thin spindle, with the rear end of which a clutch is connected and the unsupported middle part of the spindle supports a bearing bush which during the insertion of the tool into the instrument is secured against rotation with respect to the latter.

In this construction of the drilling or grinding tool, not only is an effective fixing of the cutting head with a short shank on the thin spindle ensured, but there is the further considerable advantage, that, owing to the thin spindle, even at very high speeds of revolution, which are necessary more particularly for carrying out grinding operations, no excessive heating of the bearing can occur.

The external diameter of the bearing bush corresponds preferably to the external of the usual shank of the tool, so that the new drilling and grinding tools can be used in the known hand and angle pieces.

The bearing bush or sleeve is preferably provided at its outer periphery with a lug which, on the tool being inserted into a hand or angle piece, engages in a corresponding groove of the bearing sleeve of the instrument or of the instrument itself. In this way a rotation of the bearing bush for the unsupported middle part of the spindle is prevented.

Preferably, the lug at the outer periphery of the bearing bush of the tool is so arranged that, after the insertion of the tool into the instrument, it will lie flush with a forward edge, for instance the forward edge of the instrument. In this way it is only necessary to provide the States Patent forward part of the bearing sleeve in the instrument with a groove corresponding to the length of the lug at the outer periphery of the bearing bush.

The arrangements according to the invention is illustrated by way of example in the accompanying drawing, in which:

Figure 1 shows a drilling or grinding tool in longitudinal section on line II of Figure 2;

Figure 2 the drilling or grinding tool in elevation, viewed from the side with the lug.

As will be seen from the drawing, the cutting head 1 which may be made of hard metal or be in the form of a diamond grinding member has a relatively short shank 2, in the bore of which a thin spindle 3 engages, which at its rear end carries a clutch or coupling part 4 which may be connected by means of a transverse pin 5 with the thin spindle 3. The connection of the forward end of the thin spindle 3 with the shank 2 of the cutting head 1 is preferably established by brazing.

The unsupported middle part of the thin spindle 3 carries a bearing bush 6. The bearing bush 6 is provided with a lubrication hole 7 which enables the bearing surface to be lubricated with respect to the thin spindle 3.

In the constructional form illustrated the external diameter of the bearing bush 6 corresponds to the external diameter of the usual shank of tools of a known kind, so that the drilling or grinding tools constructed in accordance with the invention can be used in the usual instruments, for instance dental hand or angle pieces.

In order to prevent any unnecessary rotary motion of the bearing bush 6 in the bearing sleeve of the instrument, the bearing bush has on its outer periphery a lug 8 which, on the tool being inserted, engages in a corresponding groove of the bearing sleeve of the instrument or of the instrument itself.

Preferably, the lug 8 is positioned on the outer periphery of the bearing bush 6 of the tool in such a manner that, after the insertion of the tool into the instrument, it will have its forward edge flush, say with the forward edge of the instrument.

I claim:

A tool unit for drilling or grinding, more particularly for dental purposes, comprising an elongated bearing bush for insertion into a hand piece and having an outer diameter corresponding to that of a normal tool arbor, to enable it to be inserted in the hand piece in lieu of said tool arbor, said bearing bush having a lug on the external periphery thereof for engagement in a groove in the hand piece to prevent rotation of the bush in the hand piece, a thin spindle rotatable in said bearing bush and projecting at both ends therefrom, a cutting head having a short shank fixed on one of said projecting ends of the thin spindle and a drive element on the opposite end of said spindle.

Eglinton Nov. 23, 1943 Kaltenbach Sept. 28, 1954 

